The present invention relates to automatic ice making machines, and more particularly to automatic ice making machines where the evaporator unit is located at a remote location from the compressor unit.
Automatic ice-making machines rely on refrigeration principles well-known in the art. During an ice making stage, the machines transfer refrigerant from the compressor unit to the evaporator unit to chill the evaporator and an ice-forming evaporator plate below freezing. Water is then run over or sprayed onto the ice-forming evaporator plate to form ice. Once the ice has fully formed, a sensor switches the machine from an ice production mode to an ice harvesting mode. During harvesting, the evaporator must be warmed slightly so that the frozen ice will slightly thaw and fall off of the evaporator plate into an ice collection bin. To accomplish this, hot refrigerant gas is routed from the compressor straight to the evaporator, bypassing the condenser.
In a typical automatic ice-making machine, the compressor unit generates a large amount of heat and noise. One of the primary advantages of a remote system is that the compressor unit may be located outdoors or in a location where the heat and noise will not be a nuisance, while the evaporator unit may be located indoors at the point where the ice is needed. This arrangement allows for the evaporator units to be placed in areas where a hot and noisy compressor previously made ice makers inconvenient or too bulky. Another advantage is that the evaporator unit by itself is smaller than a combined evaporator and compressor. Thus the evaporator unit can be located in a more compact area than an entire ice machine.
Several machines have been designed in an attempt to overcome the problem of heat and noise generated by the compressor and the condenser. In normal "remote" ice-making machines, the condenser is located at a remote location from the evaporator unit and the compressor. This allows the condenser to be located outside or in an area where the large amount of heat it generates would not be a problem. However, the compressor remains close to the evaporator unit so that it can provide the hot gas used to harvest the ice. While this machine solves the problem of heat generated by the condenser, it does not solve the problem of the noise and bulk created by the compressor.
Other machine designs place both the compressor and the condenser at a remote location. These machines have the advantage of removing both the heat and noise of the compressor and condenser to a location removed from the ice making evaporator unit. However, the compressor's distance from the evaporator unit causes inefficiency during the harvest cycle. During this cycle, hot gas from the compressor is piped directly to the evaporator unit from the compressor. Because of the length of the refrigerant lines connecting the two units in such a remote system, the hot refrigerant gas loses much of its heat before reaching the evaporator unit. This results in an increased defrost time and inefficient performance.
U.S. Pat. No. 4,276,751 to Saltzman et al. describes a compressor unit connected to one or more remote evaporator units with the use of three refrigerant lines. The first line delivers refrigerant from the compressor unit to the evaporator units, the second delivers hot gas from the compressor straight to the evaporator during the harvest mode, and the third is a common return line to carry the refrigerant back from the evaporator to the compressor. The device disclosed in the Saltzman patent has a single pressure sensor that monitors the input pressure of the refrigerant entering the evaporator units. When the pressure drops below a certain point, which is supposed to indicate that the ice has fully formed, the machine switches from an ice-making mode to a harvest mode. Hot gas is then piped from the compressor to the evaporator units. Every evaporator unit in the Saltzman device is fed by the same three common lines from the compressor unit. Whenever the compressor is piping refrigerant to one evaporator unit, it is piping refrigerant to all of the other evaporator units as well. The same is true of the hot gas in the harvest mode. Because of this, all evaporator units must be operating in the same mode. It is not possible for one evaporator unit to be in an ice-making mode while another is in a harvest mode.
U.S. Pat. No. 5,218,830 to Martineau also describes a remote ice making system. The Martineau device has a compressor unit connected to one or more remote evaporator units through two refrigerant lines, a supply line and a return line. During an ice-making mode, refrigerant passes from the compressor to the condenser, then through the supply line to the evaporator. The refrigerant vaporizes in the evaporator and returns to the compressor through the return line. During the harvest mode, a series of valves redirects hot, high pressure gas from the compressor through the return line straight to the evaporator to warm it. The cold temperature of the evaporator converts the hot gas into a liquid. The liquid refrigerant exits the evaporator and passes through a solenoid valve and an expansion device to the condenser. As the refrigerant passes through the expansion device and the condenser it vaporizes into a gas. The gaseous refrigerant then exits the condenser and returns to the compressor. As with the Saltzman et. al. patent, all evaporator units are fed by a common set of lines from the compressor unit. Thus, all evaporator units must be running in the same ice-making or harvest mode simultaneously.
One of the main drawbacks of these prior systems is that the long length of the refrigerant lines needed for remote operation causes inefficiency during the harvest mode. This is because the hot gas used to warm the evaporator must travel the length of the refrigeration lines from the compressor to the evaporator. As it travels, the hot gas loses much of its heat to the lines' surrounding environment. This results in a longer and more inefficient harvest cycle. In addition, at long distances the loss may become so great that the hot gas discharge fails to function properly at all.
Another drawback is that all of the evaporator units must be operating in the same mode simultaneously. The prior systems are limited by the use of the refrigerant lines both to circulate refrigerant in the ice-making mode and to transfer hot gas in the harvest mode. Therefore, both modes cannot be active at the same time.
All evaporator units on the prior systems must enter harvest mode simultaneously as they require the hot gas discharge from the compressor. Evaporator units,may form ice at different rates due to varying thermal characteristics. These thermodynamic characteristics will be affected by such factors as the ambient temperature of the room in which the evaporator is located, the length of the refrigerant lines from the compressor unit to the-evaporator unit, and the size and efficiency of the particular evaporator unit. Forcing all of the evaporator units to enter a harvest mode at the same time may start the harvest mode too early on some evaporator units, resulting in incompletely formed ice, and too late on others, which would decrease the production volume and energy efficiency of the system.